1. Field of the Invention
The present invention relates to thin-film magnetic heads that are used for magnetic recording of, for example, magnetic hard discs. In particular, the present invention relates to a thin-film magnetic head which meets requirements for high recording density and frequency, and a method for manufacturing the thin-film magnetic head.
2. Description of the Related Art
A known thin-film magnetic head is formed on a substantially rectangular slider 61 made of a nonmagnetic material, as shown in FIG. 1. In FIG. 20, a recording head of the known thin-film magnetic head is formed such that first and second coil layers 59 and 60, which have a laminated structure in two layers, are disposed between an upper core layer 56 and a lower core layer 57 opposing each other.
In FIG. 20, an upper magnetic-pole layer 63 and a lower magnetic-pole layer 51 sandwich a magnetic gap layer 62, the upper magnetic-pole layer 63 and the lower magnetic-pole layer 51 being disposed at ends of the upper core layer 56 and the lower core layer 57, respectively, and magnetically connected thereto.
The first coil layer 59 is disposed toward the lower core layer 57 from a reference plane S5, which is the interface where the upper magnetic layer 63 and the upper core layer 56 are joined to each other. The first coil layer 59 is covered with an insulation layer 64 of which a surface is disposed at the reference plane S5.
The second coil layer 60 is formed on the surface of the insulation layer 64 which is disposed at the reference plane S5.
Width and thickness of a coil conductor of the second coil layer 60 equal the width and thickness of the coil conductor of the first coil layer 59, respectively.
A first organic insulation-layer 58 covers the second coil layer 60 and forms an inclined face 58a toward a magnetic-disc-opposing face 61b of the slider 61. The inclined face 58a of the first organic insulation-layer 58 gradually separates from the magnetic-disc-opposing face 61b along the inclination in a film-thickness direction from the reference plane S5.
The upper core layer 56 covers the second coil layer 60 with the first organic insulation layer 58 therebetween. An end of the upper core layer 56 extends from the inclined face 58a of the first organic insulation layer 58 to an upper face of the upper magnetic-pole layer 63.
The upper core layer 56 is formed, as shown in FIG. 21, such that a conductive primary coat 70 for plating is deposited by sputtering on the first organic insulation layer 58, the primary coat 70 is coated with a resist 71, and the resist 71 is formed by photolithography into a resist frame corresponding to the shape of the upper core layer 56.
In an exposure step of photolithography for forming the resist frame, exposure light is irregularly reflected at the primary coat 70 deposited on the inclined face 58a of the first organic insulation layer 58.
When an angle formed between the inclined face 58a of the first organic insulation-layer 58 and the reference plane S5 is large, a major part of the irregularly reflected exposure light leaks toward the magnetic-disc-opposing face 61b, whereby there is a risk in that portions of the resist 71 which must be shielded are exposed.
When the angle formed between the inclined face 58a of the first organic insulation-layer 58 and the reference plane S5 is large, the resist frame cannot be formed in a shape as it is designed, and it is difficult to form the upper core layer 56 correctly in desired position and shape.
When the angle formed between the inclined face 58a of the first organic insulation-layer 58 and the reference plane S5 is large, the thickness of the first organic insulation-layer 58 is significantly reduced at corners at the outer and inner peripheries of the second coil layer 60, whereby there is a risk of a short circuit between the second coil layer 60 and the upper core layer 56. When the distance between the second coil layer 60 and the upper core layer 56 is increased without changing the shape of the second coil layer 60 in order to avoid short circuit between the second coil layer 60 and the upper core layer 56, the length of a magnetic path in the upper core layer 56 is increased; therefore, it is difficult to cope with high-frequency recording.
In the known thin-film magnetic head, the thickness of a coil conductor of the first coil layer 59 equals the thickness of the coil conductor of the second coil layer 60. Therefore, when the coil conductor of the second coil layer 60 is thick, the coil conductor of the first coil layer 59 becomes also thick. In this case, when the insulation layer 64 covering the first coil layer 59 is thin, there is a risk in that the first coil layer 59 is exposed from the insulation layer 64, whereby there is a risk in that a short circuit occurs between the first coil layer 59 and the second coil layer 60.
Accordingly, it is an object of the present invention to provide a reliable thin-film magnetic head.
The thin-film magnetic head of the present invention comprises a lower core layer; an upper core layer opposing the lower core layer; an upper magnetic-pole layer disposed between the upper core layer and the lower core layer and joined to the upper core layer; a magnetic gap layer disposed between the upper magnetic-pole layer and the lower core layer; a first coil layer disposed at the lower core layer side of an interface between the upper core layer and the upper magnetic-pole layer, which are joined to each other; and a second coil layer disposed at the upper core layer side of the interface. The thickness of a coil conductor of the first coil layer is smaller than the thickness of a coil conductor of the second coil layer.
With this arrangement, the first coil layer can be formed at a sufficiently large distance from the interface between the upper magnetic-pole layer and the upper core layer by reducing the thickness of the coil conductor of the first coil layer, whereby a reliable thin-film magnetic head is obtainable, in which insulation between the first and second coil layers is ensured. In the thin-film magnetic head according to the present invention, the interface between the upper magnetic-pole layer and the upper core layer can be lowered because the first coil layer is disposed at a sufficiently large distance from the interface, whereby the thickness of the upper magnetic-pole layer can be reduced. By reducing the thickness of the upper magnetic-pole layer, magnetic fluxes can flow efficiently from the upper core layer to the magnetic gap layer; therefore, the thin-film magnetic head can cope with high recording density.
The width of the coil conductor of the second coil layer may be smaller than the width of the coil conductor of the first coil layer.
By increasing the thickness and reducing the width of the coil conductor of the second coil layer, a proper number of windings can be provided in a reduced area without increasing DC resistance in the coil conductor. Therefore, the length of the upper core layer from a part of the second coil layer in the vicinity of a coil center thereof to the periphery of the second coil layer can be reduced, whereby the length of a magnetic path is reduced, thereby providing a thin-film magnetic head having low inductance and capable of high-frequency recording.
When the thickness of the first coil layer is reduced corresponding to the reduction of thickness of the upper magnetic-pole layer in accordance with requirements for high recording density, DC resistance in the first coil layer is maintained at a low level by increasing the width of the coil conductor of the first coil layer. Therefore, a thin-film magnetic head can be provided, in which power loss in the first coil layer is suppressed.
The distance between each winding of the coil conductor of the second coil layer may be smaller than the distance between each winding-of the coil conductor of the first coil layer.
With this arrangement, the length of the upper core layer from a part of the second coil layer in the vicinity of the coil center thereof to the periphery of the second coil layer is further reduced, and the magnetic path is thereby further reduced, whereby a thin-film magnetic head having low inductance and capable of high-frequency recording can be provided.
The ratio of the thickness of the coil conductor of the first coil layer to the thickness of the coil conductor of the second coil layer may be not greater than 0.8.
The thin-film magnetic head offers an advantage in that the first and second coil layers can be sufficiently separated from each other by reducing the thickness of the coil conductor of the first coil layer while the thickness of the coil conductor of the second coil layer is maintained so that the DC resistance in the second coil layer is maintained at a low level.
The ratio of the width of the coil conductor of the first coil layer to the width of the coil conductor of the second coil layer may be not smaller than 1.2.
The thin-film magnetic head offers another advantage in that the second coil layer can be formed in a reduced area by reducing the width of the coil conductor of the second coil layer while the width of the coil conductor of the first coil layer is maintained so that the DC resistance in the first coil layer is maintained at a low level when the thickness of the coil conductor of the first coil layer is reduced.
The ratio of the distance between each winding of the coil conductor of the first coil layer to the distance between each winding of the coil conductor of the second coil layer may be not smaller than 1.2.
With this arrangement, the area in which the second coil layer is formed can be further reduced.
In the thin-film magnetic head according to the present invention, a first organic insulation-layer which covers the second coil layer may be provided. The first organic insulation-layer may include an inclined face formed at an end thereof toward a magnetic-medium-opposing face, the inclined face being inclined so as to be gradually separated from a magnetic medium along the inclination in the film-thickness direction such that an angle between the inclined face and the interface between the first organic insulation-layer and the second coil layer is not greater than 60 degrees.
With this arrangement, a resist frame can be formed in predetermined shape and position in a step of forming the resist frame which encloses the upper core layer at a margin thereof by exposing and developing a resist film applied to the first organic insulation-layer. Therefore, the upper core layer can be formed in predetermined shape and position by being formed in a region enclosed by the resist frame.
The lower core layer may be provided with a lower magnetic-pole layer formed at an end of the lower core layer, the lower magnetic-pole layer projecting toward the upper magnetic-pole layer, and the magnetic gap layer may be formed between the upper magnetic-pole layer and the lower magnetic-pole layer.
With this arrangement, leakage magnetic fluxes, which are produced at the magnetic gap layer between the upper and lower magnetic-pole layers, are not likely to be produced at a position separated from a position between the upper and lower magnetic-pole layers, whereby a thin-film magnetic head having high recording density, in which write fringes are suppressed, is obtainable.
In the thin-film magnetic head according to the present invention, an end face of the upper core layer toward a magnetic medium may be formed as an inclined face which is inclined so as to be gradually separated from the magnetic medium along the inclination in the film-thickness direction from the upper magnetic-pole layer.
With this arrangement, the area of the interface between the upper core layer and the upper magnetic-pole layer joined to each other can be increased, in which the upper core layer is not exposed from the upper magnetic-pole layer, whereby magnetic fluxes as leakage fluxes from a magnetic field induced in the upper core layer can be effectively applied to a magnetic medium.
The lower core layer may be provided thereon with an insulative part for setting a gap depth, and a rear end of the magnetic gap layer may be in contact with the insulative part for setting the gap depth.
The magnetic gap layer can be formed so as to have a proper depth in accordance with the width of a gap and the shape of the magnetic gap layer by using the insulative layer for setting a gap depth.
In the thin-film magnetic head according to the present invention, a second organic insulation-layer may be applied to the first coil layer between each winding of the coil conductor thereof. A second inorganic insulation-layer may cover the overall surface of the second organic insulation-layer, a surface of the second inorganic insulation-layer being formed planar. The second coil layer may be formed on the planar surface of the second inorganic insulation-layer.
With this arrangement, production of gaps in the second inorganic insulation-layer can be suppressed by the second organic insulation-layer being applied to the first coil layer between each winding of the coil conductor of the first coil layer, whereby deformation due to inflation of gas disposed in the gaps can be avoided. Therefore, a reliable thin-film magnetic head is obtainable.
Since the surface of the second inorganic insulation-layer can be made flat by polishing, the second coil layer can be formed accurately in desired shape and position on the second inorganic insulation-layer.
The first coil layer may be formed on a surface of a first inorganic insulation-layer, and the second inorganic insulation-layer may be formed such that the distance from the first inorganic insulation-layer to the second inorganic insulation-layer disposed between each winding of the coil conductor of the first coil layer is greater than the distance between each winding of the coil conductor of the first coil layer.
With this arrangement, production of the gaps in the second inorganic insulation-layer can be more reliably suppressed.
The second inorganic insulation-layer may comprise one of Al2O3 and SiO3, and the second organic insulation-layer may comprise one of a novolak resin and a polyimide resin.
The first coil layer is applied with the second organic insulation-layer so that the second inorganic insulation-layer easily enters between each winding of the coil conductor of the first coil layer, and the surface of the second inorganic insulation-layer is easily polished to be flat and smooth.
The magnetic gap layer may comprise a nonmagnetic metal capable of being formed by electrolytic plating.
Since at least the magnetic gap layer and the upper magnetic-pole layer can be formed continuously by electrolytic plating, manufacturing processes can be simplified. The nonmagnetic metal which can be formed by electrolytic plating may be selected from NiP, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.
A method for manufacturing a thin-film magnetic head according to the present invention comprises the steps of forming a magnetic gap layer on a lower core layer; forming an upper magnetic-pole layer on the magnetic gap layer; forming a first coil layer on the lower core layer; forming a second inorganic insulation-layer which covers the first coil layer; polishing upper surfaces of the second inorganic insulation-layer and the upper magnetic-pole layer such that the upper surfaces are formed planar and are disposed continuously on the same plane; forming a second coil layer on the second inorganic insulation-layer after polishing the upper surfaces of the second inorganic insulation-layer and the upper magnetic-pole layer, the thickness of a coil conductor of the second coil layer being greater than the thickness of a coil conductor of the first coil layer; forming a first organic insulation-layer for covering the second coil layer; forming a fourth resist frame on the first organic insulation-layer, for enclosing an upper core layer at the periphery thereof; and forming the upper core layer in a region enclosed by the fourth resist frame. The fourth resist frame is formed in such a manner that a resist applied to the first organic insulation-layer is exposed in a pattern of the fourth resist frame.
In the method for manufacturing a thin-film magnetic head, an end face of the upper core layer toward a magnetic-disc-opposing face can be formed as an inclined face which is inclined so as to be separated from a magnetic medium gradually along the inclination in a film-thickness direction.
The method for manufacturing a thin-film magnetic head further comprises the step of forming a second organic insulation-layer after forming the first coil layer, the first coil layer being filled with the second organic insulation-layer entering between each winding of a coil conductor of the first coil layer. The second inorganic insulation-layer is formed by sputtering on a surface of the second organic insulation-layer.
In the method for manufacturing a thin-film magnetic head, the second inorganic insulation-layer can be formed without gaps.
The method for manufacturing a thin-film magnetic head further comprises the step of forming an insulative layer for setting a gap depth on the lower core layer. The magnetic gap layer is formed after the insulative layer for setting a gap depth is formed.
In the method for manufacturing a thin-film magnetic head, the depth of the magnetic gap layer can be set correctly.